1. Field of the Invention
The present invention relates to a recording and reproducing apparatus for recording a video signal together with indexing information to tape, and for reproducing the recorded information by means of rotating heads, and particularly to a recording and reproducing apparatus for recording editable indexing information.
2. Description of the Prior Art
Video cassette recorders (VCR) and other recording and reproducing apparatuses using a tape medium are now widely and commonly available. Further reductions in device size enabled by high density recording techniques and digital technologies are also being developed. In digital media such as these, a subcode is usually also recorded when recording the data signal. This subcode is an integral part of the complete data signal, and may be or include an indexing ID showing the recording start position of the data, an absolute time code showing the absolute position of the data on tape, or a user-defined time code. Examples of devices recording such a subcode include DAT (Digital Audio Tape recorders) and 8 mm VCRs. It is commonly known that the DAT and 8 mm VCR standards specify an editable subcode that can be separately re-recorded while preserving the recorded video signal and audio signal.
The following problems, however, have existed with this conventional subcode, particularly when rewriting the indexing information.
For example, let us assume that a 9-sec. indexing ID is recorded to a certain position on tape. The fixed (predetermined) recording time of the indexing ID is determined with respect to the signal detection capacity during high speed searches, and it follows that the detection capacity increases relative to the length of the indexing ID recording time. This characteristic is particularly strong when the indexing ID is recorded to part of a diagonal track. If new indexing information is then recorded starting from some position in the fixed length recording time of this indexing ID (for example, at the position 4 sec. from the start of the indexing ID recording period), the existing indexing ID is edited and this new indexing ID is recorded for 9 sec. from that position. As a result of recording this new indexing ID for 9 sec., a continuous indexing ID recording period 13 sec. in duration is effectively recorded to the tape by means of this prior art method. The problem with this method is that it becomes no longer possible to accurately determine the recording start position of the new indexing ID.
It is also possible that when recording a new indexing ID for this 9-sec. period, this fixed length period may overlap the starting position of a previously recorded indexing ID. For example, a previously recorded indexing ID may have been recorded for the standard 9 sec. period starting from a position 4 sec. from the start of a newly recorded indexing ID. Recording this new indexing ID for 9 sec. will likewise result in a continuous indexing ID recording period 13 sec. in duration being recorded to the tape. A similar problem again results: it is not possible to accurately determine the recording start position of the previously recorded indexing ID.
The above two problems become extremely inconvenient when the recording start position of the indexing ID is particularly meaningful (e.g., when the indexing ID identifies a scene or selection change). The starting position of editing operations intended to start from this indexing ID will therefore be offset, and the ID will be effectively rendered useless for precision editing tasks.